RCA Theremin Service Notes

(12) METHODS FOR CONTINUITY TESTS

In making a continuity test whether it be for the Theremin assembly or the S. P. U., the following procedure is recommended:
Disconnect the cable connecting the socket power unit to the Theremin assembly, the loudspeaker, and the A.C. supply cord at its outlet.
A pair of headphones, with at least 41/2 volts in series, or preferably a voltmeter with sufficient voltage to give a full scale deflection when connected across the battery terminals, should be used in making these tests, for example, a 0-50 volt meter with a 4,5volt “B” battery. The Radiotron socket contacts, numbers and lugs used in these tests are shown in Figure 6. The Theremin continuity wiring diagram is illustrated in Figure 8, the S. P. U. terminal numbers are shown in Figure 7.
Test leads should be of the flexible insulated type with partially insulated testing tips, so that false readings will not be obtained through contact with the hands. Similarly the hand should not touch the chassis or component parts.
The contacts of the test equipment should be placed across the terminals or leads indicated in the following test table under the column marked “Terminals.” If the results are negative the cause of such negative effect will be found in the last column under the heading, “Incorrect Effect Caused By.” The second column indicates the approximate correct resistance in ohms of most of the circuits tested.

(13) S.P.U. CONTINUITY TESTS

Remove UX-280 Radiotron and Disconnect Cable -Refer to Figure 8